Rotaviruses belong to the Reoviridae family of viruses, and can affect the gastrointestinal system and the respiratory tract of birds, amongst other organisms. The family of Reoviridae consists of different genera including orthoreovirus (avian and mammalian reoviruses), orbivirus (Bluetongue virus) and rotavirus (groups A to G).
Rotaviruses are non-enveloped, double-shelled RNA viruses. The genome is composed of 11 segments of double-stranded RNA, which code for six structural and six non-structural proteins.
There are six viral proteins (VPs) that form the three-layered icosahedral protein capsid of the virion. These structural proteins are called VP1, VP2, VP3, VP4, VP6 and VP7 [1]. VP6 forms the bulk of the capsid. It is highly antigenic and can be used to identify rotavirus species [2]. In addition to the VPs, there are six non-structural proteins (NSPs) that are only produced in cells infected by rotavirus. These are called NSP1, NSP2, NSP3, NSP4, NSP5 and NSP6 [1].
Avian rotaviruses (ARVs) are well known [3, 4 and 5] and frequently affect poultry flocks, and in particular chicken flocks, worldwide. The symptoms in infected chicken are diarrhoea with subsequent slow weight gain, a syndrome which is known as Malabsorption Syndrome (MAS) or Runting Stunting Syndrome (RSS).
In one field study, broiler chicks between 6 and 18 days of age from 8 flocks with RSS were examined to determine which ARVs are major contributors to the pathogenesis of RSS [6]. In this study, ARVs were detected in 32 of 34 chicks from the flocks with RSS. Four groups of ARVs were identified in flocks with RSS: AVR A, D, F and G. The results of this study showed that group D ARV plays a major role in the pathogenesis of RSS.
The economic impact of RSS on chicken breeders is severe. All infected chickens will be lost. Early detection and prevention of infection by ARV is therefore highly desirable.
Currently, ARVs are usually detected and identified on the basis of the migration of the 11 genomic RNA fragments using RNA-PAGE. The RNA-PAGE pattern characteristic of an group D ARV is 5:2:2:2 [7]. This characteristic pattern of RNA migration can be used to identify group D ARVs.
ARVs can also be detected using ELISA [8], transmission electron microscopy, and reverse-transcriptase polymerase chain reaction (RT-PCR) [6]. Only PAGE allows discrimination of different ARV groups, but it has only a low degree of sensitivity. At present, PCR methods are only available for detection of group A rotaviruses. No nucleotide sequence data existed for group D ARVs at the priority date. There is therefore a pressing need to develop alternative methods of the detection of other rotaviruses, and in particular group D rotaviruses. In particular, there is a pressing need to develop a rapid and sensitive detection method for group D ARVs.